EP0150456A2 - Vieillissement à température relativement basse d'un alliage d'aluminium, contenant du lithium - Google Patents

Vieillissement à température relativement basse d'un alliage d'aluminium, contenant du lithium Download PDF

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Publication number
EP0150456A2
EP0150456A2 EP84115925A EP84115925A EP0150456A2 EP 0150456 A2 EP0150456 A2 EP 0150456A2 EP 84115925 A EP84115925 A EP 84115925A EP 84115925 A EP84115925 A EP 84115925A EP 0150456 A2 EP0150456 A2 EP 0150456A2
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Prior art keywords
alloy
aluminum
lithium
percent
aged
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EP84115925A
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German (de)
English (en)
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EP0150456A3 (en
EP0150456B1 (fr
Inventor
R. Eugene Curtis
G. Hari Narayanan
William E. Quist
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Boeing Co
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Boeing Co
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium

Definitions

  • the present invention relates to aluminum alloys, more particularly to aluminum alloys containing lithium as an alloying element, and most particularly to a process for improving the fracture toughness of aluminum-lithium alloys without detracting from their strength.
  • aluminum-lithium alloys have been used only sparsely in aircraft structure.
  • the relatively low use has been caused by casting difficulties associated with aluminum-lithium alloys and by their relatively low fracture toughness compared to other more conventional aluminum alloys.
  • Aluminum-lithium alloys provide a substantial lowering of the density of aluminum alloys (as well as a relatively high strength to weight ratio), which has been found to be very important in decreasing the overall weight of structural materials used in an aircraft. While substantial strides have been made in improving the aluminum-lithium processing technology, a major challenge is still to obtain a good blend of fracture toughness and high strength with an aluminum-lithium alloy.
  • the present invention provides a method for aging aluminum-lithium alloys of various composition at relatively low temperatures to develop a high fracture toughness without reducing the strength of the alloy to any significant extent.
  • the alloy is aged at a relatively low temperature for a relatively long time. This process may be generally referred to as low temperature underaging. More specifically, the alloy can be aged at temperatures ranging from 200° F to 300° F for a period of time ranging from 1 up to 70 or more hours.
  • This low temperature aging regimen will result in an alloy having a strength level generally equivalent to or only slightly lower than that of peak aged material while maintaining a fracture toughness on the order of 150 to 200 percent greater than that of materials aged at conventional higher temperatures.
  • An aluminum-lithium alloy formulated in accordance with the present invention can contain from about 1.0 to about 3.2 percent lithium.
  • the current data indicates that the benefits of the low temperature aging are most apparent at lithium levels of 2.7 percent and below. All percentages herein are by weight percent based on the total weight of the alloy unless otherwise indicated.
  • Additional alloying agents such as magnesium and copper can also be included in the alloy.
  • the magnesium in the alloy functions to increase strength and slightly decrease density. It also provides solid solution strengthening.
  • the copper adds strength to alloy, but unfortunately also serves to increase density.
  • Grain refiners such as zirconium can also be also be included.
  • Manganese can also be present alone or together with zirconium. The manganese functions to provide an improved combination of strength and fracture toughness.
  • Iron and silicon can each be present in amounts up to 0.3 percent. It is preferred, however, that these elements be present only in trace amounts of less than 0.10 percent. Certain trace elements such as zinc may be present in amounts up to but not to exceed 0.25 percent. Certain other trace elements such as chromium must be held to levels of 0.05 percent or less. If these maximums are exceeded, the desired properties of the aluminum-lithium alloy will tend to deteriorate.
  • the trace elements sodium and hydrogen are also thought to be harmful to the properties (fracture toughness in particular) of aluminum-lithium alloys and should be held to the lowest levels practically attainable, for example on the order of 15 to 30 ppm (0.0015-0.0030 wt. %) for the sodium and less than 15 ppm (0.0015 wt. %) and preferably less than 1.0 ppm (0.0001 wt. %) for the hydrogen.
  • the balance of the alloy comprises aluminum.
  • the following table represents the proportions in which the alloying and trace elements may be present.
  • the broadest ranges are acceptable under most circumstances, while the preferred ranges provide a better balance of fracture toughness, strength and corrosion resistance.
  • the most preferred ranges yield alloys that presently provide the best set of overall properties for use in aircraft structure.
  • a most preferred alloy that is especially susceptible to property enhancement in accordance with the techniques of the present invention is an alloy containing 2.2 to 2.8 percent lithium, 0.4 to 0.8 percent magnesium, 1.5 to 2.1 percent copper and up to 0.15 percent zirconium as a grain refiner.
  • the preferred limitations on iron, silicon and other trace elements also applies to this preferred alloy.
  • An aluminum-lithium alloy formulated in the proportions set forth in the foregoing paragraphs is processed into an article utilizing known techniques.
  • the alloy is formulated in molten form and cast into an ingot.
  • the ingot is then homogenized at temperatures ranging from 925 F to 1000° F.
  • the alloy is converted into a usable article by conventional mechanical formation techniques such as rolling, extrusion or the like.
  • the alloy is normally subjected to a solution treatment at temperatures ranging from 950° F to 1000° F, quenched in a quenching medium such as water that is maintained at a temperature on the order of 70° F to 150° F. If the alloy has been rolled or extruded, it is generally stretched on the order of 1 to 3 percent of its original length to relieve internal stresses.
  • the aluminum alloy can then be further worked and formed into the various shapes for its final application. Additional heat treatments such as solution heat treatment can be employed if desired. For example, an extruded product after being cut to desired length are generally solution heat treated at temperatures on the order of 975° F for 1 to 4 hours. The product is then quenched in a quenching medium held at temperatures ranging from about 70 0 F to 150° F.
  • the article is subjected to an aging treatment that will increase the strength of the material, while maintaining its fracture toughness and other engineering properties at relatively high levels.
  • the articles are subjected to a low temperature underage heat treatment at temperatures ranging from about 200 0 F to about 300° F. It is preferred that the alloy be heat treated in the range of from about 250° F to 275° F. At the higher temperatures, less time is needed to bring about the proper balance between strength and fracture toughness than at lower aging temperatures, but the overall property mix will be slightly less desirable.
  • the aging when the aging is conducted at temperatures on the order of 275° F to 300° F, it is preferred that the product be subjected to the aging temperature for periods of from 1 to 40 hours. On the other hand, when aging is conducted at temperatures on the order of 250° F or below, aging times from 2 to 80 hours or more are preferred to bring about the proper balance between fracture toughness and strength. After the aging treatment, the aluminum-lithium articles are cooled to room temperature.
  • the treatment will result in an aluminum-lithium alloy having an ultimate strength on the order of 65 to 95 ksi, depending on the detail composition of the alloy.
  • the fracture toughness of the material will be on the order of 1 1/2 to 2 times greater than that of similar aluminum-lithium alloys subjected to conventional aging treatments, which are normally conducted at temperatures greater than 300° F .
  • the superior strength and toughness combination achieved by the low temperature underaging techniques in accordance with the present invention also surprisingly causes some aluminum-lithium alloys to exhibit an improvement in stress corrosion resistance when contrasted with the same alloy aged by standard aging practices. Examples of these improved characteristics will be set forth in more detail in conjunction with the ensuing examples.
  • An aluminum alloy containing 2.4 lithium, 1 percent magnesium, 1.3 percent copper, 0.15 percent zirconium with the balance being aluminum was formulated.
  • the trace elements present in the formulation constituted less than 0.25 percent of the total.
  • the iron and silicon present in the formulation constituted less than 0.07 percent each of the formulation.
  • the alloy was cast and homogenized at 975° F. Thereafter, the alloy was hot rolled to a thickness of 0.2 inches. The resulting sheet was then solution treated at 975° F for about 1 hour. It was then quenched in water maintained at about 70° F. Thereafter, the sheet was subjected to a stretch of 1 1/2 percent of its initial length and then material was then cut into specimens.
  • the specimens were cut to a size of 0.5 inch by 2 1/2 inch by 0.2 inch for the precrack Charpy impact tests, a known method of measuring fracture toughness.
  • the specimens prepared for the tensile strength tests were 1 inch by 4 inches by 0.2 inches.
  • a plurality of specimens were then aged at 350° F for 4, 8 and 16 hours; at 325° F for 8, 16, and 48 hours; at 305° F for 8 hours; at 275OF for 16 and 40 hours; and at 250° F for 40 and 72 hours.
  • Each of the specimens aged at each of the temperatures and times were then subjected to the tensile strength and precrack Charpy impact tests in accordance with standard testing procedures.
  • the values of each of the specimens aged at a particular time and temperatures were then averaged. These average values are set forth in the graph of FIGURE 1.
  • FIGURE 1 By observing FIGURE 1 it will be readily observed that specimens aged at temperatures greater than 300° F exhibit a toughness on the order of from 225 to 525 inch-pounds per square inch as measured by the Charpy impact test. By contrast, the specimens underaged at a low temperature in accordance with the present invention exhibit toughnesses on the order of 650 to almost 850- inch pounds per square inch as indicated by the Charpy impact test. At the same time, the average strength of the materials fall generally within the 64 to 71 ksi range, with the exception of the specimens aged at 350° F for 16 hours. These specimens, however, exhibited the lowest toughness of any of the specimens.
  • An aluminum alloy containing from 2 percent lithium, 1 percent magnesium, 2.5 percent copper, 0.15 percent zirconium, and the balance aluminum was formulated.
  • the trace elements totaled less than 0.25 percent of the total composition, while the iron and silicon were maintained at less than 0.07 percent of the total formulation.
  • the alloy was cast and homogenized at a temperature of about 975° F.
  • the alloy was then extruded into a bar having cross-sectional dimensions of 0.75 inch by 2.5 inch.
  • the bar was then cut into predetermined lengths and solution heat treated at about 975° F for 1 hour. Thereafter, the articles were quenched in either 70° F or 180 0 F water. Once the bars had cooled, they were stretched approximately 1 1/2 percent of their original length.
  • the bars were then fabricated into double cantilever bean (DCB) test specimens for measuring crack growth velocity during stress corrosion cracking. These specimens have a length of approximately six (6) inches.
  • DCB double cantilever bean

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  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Organic Chemistry (AREA)
  • Metallurgy (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Forging (AREA)
  • Heat Treatment Of Steel (AREA)
  • Conductive Materials (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)
EP84115925A 1983-12-30 1984-12-20 Vieillissement à température relativement basse d'un alliage d'aluminium, contenant du lithium Expired - Lifetime EP0150456B1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US56722783A 1983-12-30 1983-12-30
US567227 1983-12-30

Publications (3)

Publication Number Publication Date
EP0150456A2 true EP0150456A2 (fr) 1985-08-07
EP0150456A3 EP0150456A3 (en) 1986-10-08
EP0150456B1 EP0150456B1 (fr) 1990-11-14

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EP84115925A Expired - Lifetime EP0150456B1 (fr) 1983-12-30 1984-12-20 Vieillissement à température relativement basse d'un alliage d'aluminium, contenant du lithium

Country Status (4)

Country Link
US (1) US4840682A (fr)
EP (1) EP0150456B1 (fr)
JP (1) JPH0660371B2 (fr)
DE (1) DE3483607D1 (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0227563A1 (fr) * 1985-11-28 1987-07-01 Cegedur Pechiney Rhenalu Procédé de désensibilisation à la corrosion exfoliante avec obtention simultanée d'une haute résistance mécanique et bonne tenue aux dommages des alliages d'aluminium contenant du lithium
US4861391A (en) * 1987-12-14 1989-08-29 Aluminum Company Of America Aluminum alloy two-step aging method and article
US4869870A (en) * 1988-03-24 1989-09-26 Aluminum Company Of America Aluminum-lithium alloys with hafnium
US4961792A (en) * 1984-12-24 1990-10-09 Aluminum Company Of America Aluminum-lithium alloys having improved corrosion resistance containing Mg and Zn
US5066342A (en) * 1988-01-28 1991-11-19 Aluminum Company Of America Aluminum-lithium alloys and method of making the same
US5085830A (en) * 1989-03-24 1992-02-04 Comalco Aluminum Limited Process for making aluminum-lithium alloys of high toughness
US5108519A (en) * 1988-01-28 1992-04-28 Aluminum Company Of America Aluminum-lithium alloys suitable for forgings
US5137686A (en) * 1988-01-28 1992-08-11 Aluminum Company Of America Aluminum-lithium alloys
US5422066A (en) * 1989-03-24 1995-06-06 Comalco Aluminium Limited Aluminum-lithium, aluminum-magnesium and magnesium-lithium alloys of high toughness

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4999061A (en) * 1983-12-30 1991-03-12 The Boeing Company Low temperature underaging of lithium bearing alloys and method thereof
EP0151301B1 (fr) * 1983-12-30 1989-06-07 The Boeing Company Alliage aluminium-lithium
CA1337747C (fr) * 1986-12-01 1995-12-19 K. Sharvan Kumar Alliages ternaires aluminium-lithium
JPH0814018B2 (ja) * 1987-12-14 1996-02-14 アルミニウム カンパニー オブ アメリカ アルミニウム合金の熱処理方法
US5462712A (en) * 1988-08-18 1995-10-31 Martin Marietta Corporation High strength Al-Cu-Li-Zn-Mg alloys
US5455003A (en) * 1988-08-18 1995-10-03 Martin Marietta Corporation Al-Cu-Li alloys with improved cryogenic fracture toughness
US5512241A (en) * 1988-08-18 1996-04-30 Martin Marietta Corporation Al-Cu-Li weld filler alloy, process for the preparation thereof and process for welding therewith
US5211910A (en) * 1990-01-26 1993-05-18 Martin Marietta Corporation Ultra high strength aluminum-base alloys
US5133931A (en) * 1990-08-28 1992-07-28 Reynolds Metals Company Lithium aluminum alloy system
US5198045A (en) * 1991-05-14 1993-03-30 Reynolds Metals Company Low density high strength al-li alloy
ES2445745T3 (es) 1997-09-22 2014-03-05 Eads Deutschland Gmbh Aleación sobre una base de aluminio y procedimiento para su tratamiento térmico
US7056395B1 (en) * 1999-09-01 2006-06-06 Brush Wellman, Inc. Dies for die casting aluminum and other metals
US6368427B1 (en) * 1999-09-10 2002-04-09 Geoffrey K. Sigworth Method for grain refinement of high strength aluminum casting alloys
US7105067B2 (en) * 2003-06-05 2006-09-12 The Boeing Company Method to increase the toughness of aluminum-lithium alloys at cryogenic temperatures
BRPI0820679A2 (pt) 2007-12-04 2019-09-10 Alcoa Inc ligas alumínio-cobre-lítio melhoradas
US8333853B2 (en) * 2009-01-16 2012-12-18 Alcoa Inc. Aging of aluminum alloys for improved combination of fatigue performance and strength
CN112646994B (zh) * 2020-12-16 2022-03-04 中南大学 一种高比强高比模铝合金及其制备方法

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB787665A (en) * 1955-04-05 1957-12-11 Stone & Company Charlton Ltd J Improvements relating to aluminium-base alloys
US2915391A (en) * 1958-01-13 1959-12-01 Aluminum Co Of America Aluminum base alloy
GB2115836A (en) * 1982-02-26 1983-09-14 Secr Defence Improvements in or relating to aluminium alloys
EP0090583A2 (fr) * 1982-03-31 1983-10-05 Alcan International Limited Traitement thermique d'alliages d'aluminium
EP0124286A1 (fr) * 1983-03-31 1984-11-07 Alcan International Limited Alliages d'aluminium

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS602644A (ja) * 1983-03-31 1985-01-08 アルカン・インタ−ナシヨナル・リミテイド アルミニウム合金

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB787665A (en) * 1955-04-05 1957-12-11 Stone & Company Charlton Ltd J Improvements relating to aluminium-base alloys
US2915391A (en) * 1958-01-13 1959-12-01 Aluminum Co Of America Aluminum base alloy
GB2115836A (en) * 1982-02-26 1983-09-14 Secr Defence Improvements in or relating to aluminium alloys
EP0090583A2 (fr) * 1982-03-31 1983-10-05 Alcan International Limited Traitement thermique d'alliages d'aluminium
EP0124286A1 (fr) * 1983-03-31 1984-11-07 Alcan International Limited Alliages d'aluminium

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
ALUMINIUM-LITHIUM ALLOYS II, CONFERENCE PROCEEDINGS OF ALUMIMIUM-LITHIUM ALLOYS II, Monterey, US, 12th-14th April 1983, pages 363-391, AIME, Warrendale, US; PEEL et al.: "The development and application of improved alumimium-lithium alloys" *
ALUMINIUM-LITHIUM ALLOYS II, CONFERENCE PROCEEDINGS OF ALUMINIUM-LITHIUM ALLOYS II, Monterey, US, 12th-14th April 1983, pages 219-233, AIME, Warrendale, US; HARRIS et al.: "Effect of composition and heat treatment on strength and fracture characteristics of Al-Li-Mg alloys *
ALUMINIUM-LITHIUM ALLOYS II, CONFERENCE PROCEEDINGS OF ALUMINIUM-LITHIUM ALLOYS II, Monterey, US, 12th-14th April 1983, pages 393-405, AIME, Warrendale, US; SANKARAN et al.: "Structure-property relationships in Al-Cu-Li alloys" *
CHEMICAL ABSTRACTS, vol. 78, no. 20, 21st May 1973, page 217, abstract no. 127717e, Columbus, Ohio, US; A. CHERNYAK et al.: "Mechanical properties of 01420 aluminum alloy sheet after aging", & METALLOVED. TERM. OBRAB. METAL. (1973), (1), 75-6 *

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4961792A (en) * 1984-12-24 1990-10-09 Aluminum Company Of America Aluminum-lithium alloys having improved corrosion resistance containing Mg and Zn
EP0227563A1 (fr) * 1985-11-28 1987-07-01 Cegedur Pechiney Rhenalu Procédé de désensibilisation à la corrosion exfoliante avec obtention simultanée d'une haute résistance mécanique et bonne tenue aux dommages des alliages d'aluminium contenant du lithium
US4861391A (en) * 1987-12-14 1989-08-29 Aluminum Company Of America Aluminum alloy two-step aging method and article
US5066342A (en) * 1988-01-28 1991-11-19 Aluminum Company Of America Aluminum-lithium alloys and method of making the same
US5108519A (en) * 1988-01-28 1992-04-28 Aluminum Company Of America Aluminum-lithium alloys suitable for forgings
US5137686A (en) * 1988-01-28 1992-08-11 Aluminum Company Of America Aluminum-lithium alloys
US4869870A (en) * 1988-03-24 1989-09-26 Aluminum Company Of America Aluminum-lithium alloys with hafnium
US5085830A (en) * 1989-03-24 1992-02-04 Comalco Aluminum Limited Process for making aluminum-lithium alloys of high toughness
US5422066A (en) * 1989-03-24 1995-06-06 Comalco Aluminium Limited Aluminum-lithium, aluminum-magnesium and magnesium-lithium alloys of high toughness

Also Published As

Publication number Publication date
DE3483607D1 (de) 1990-12-20
EP0150456A3 (en) 1986-10-08
JPS60215750A (ja) 1985-10-29
JPH0660371B2 (ja) 1994-08-10
US4840682A (en) 1989-06-20
EP0150456B1 (fr) 1990-11-14

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